/*
 * Copyright (c) 2011-2012 Alexander Dubu
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 * o  Redistributions of source code must retain the above copyright notice,
 *    this list of conditions and the following disclaimer.
 *
 * o  Redistributions in binary form must reproduce the above copyright notice,
 *    this list of conditions and the following disclaimer in the documentation
 *    and/or other materials provided with the distribution.
 *
 * o  Neither the name Axil nor the names of its contributors may be used to
 *    endorse or promote products derived from this software without specific
 *    prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */
package axil.stdlib.statistics.function;

import axil.api.AxilObject;
import axil.stdlib.core.type.Nil;
import axil.stdlib.numbers.type.Int;
import axil.stdlib.numbers.type.Num;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.Map;


/**
 * Find the value that is the least common in a collection of values. If there
 * is more than one value with the same statistical distribution, then a value
 * is selected at random.
 */
public class LeastCommon extends ComplexListCalculation {
    /**
     * This is the result that should be returned if nothing is passed to the function;
     * if the parameter size is zero. The default is to return zero.  Some may choose to return Nil.
     */
    protected AxilObject zeroResult()
    {
        return Nil.object;
    }

    /**
     * Execute the specific statistical function against the given arguments.
     */
    protected AxilObject calculate(ArrayList<Num> values) {
        final int size = values.size();
        final Int sizeN = Int.from(size);
        if (size == 0) {
            return zeroResult();
        }
        // Store a count for each unique value.
        Map<AxilObject, Integer> commonMapping = new HashMap<AxilObject, Integer>();
        for(AxilObject nextValue : values) {
            Integer count = commonMapping.get(nextValue);
            if (count == null) {
                count = Integer.valueOf(1);
            } else {
                count = Integer.valueOf(count.intValue() + 1);
            }
            commonMapping.put(nextValue, count);
        }
        // Find the lowest count (for any of the values).
        int leastCount = Integer.MAX_VALUE;
        for(Integer nextCount : commonMapping.values()) {
            int count = nextCount.intValue();
            if (count < leastCount)
            {
                leastCount = count;
            }
        }
        // Return the first value that matches the max count
        for(AxilObject nextValue : values) {
            int count = commonMapping.get(nextValue).intValue();
            if (count == leastCount)
            {
                return nextValue;
            }
        }
        return zeroResult();
    }
}
